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Why Sirius fools so many UFO witnesses

Sirius can flash red, green and blue near the horizon, making a fixed winter star look like a hovering craft.

On this page

  • Why Sirius is a repeat UFO suspect
  • Low horizon colour flashing from the UK
  • How to test a Sirius match in a case file
Preview for Why Sirius fools so many UFO witnesses

Introduction

Few astronomical objects generate more “hovering UFO” reports in the UK than Sirius. The reason is not mysterious once the viewing conditions are understood. Sirius is the brightest true star visible from Earth, and from British latitudes it spends much of the winter sitting relatively low above the southern horizon. That combination makes it unusually vulnerable to atmospheric distortion. To a witness unfamiliar with the effect, Sirius can appear to pulse, flash red and green, shimmer like a beacon, or even seem to drift and manoeuvre. [Sky & Telescope]skyandtelescope.orgsirius ly scintillating holiday12222014Sky & TelescopeHave a Sirius-ly Scintillating Holiday!22 Dec 2014 — Sirius twinkles more than most stars because it's bright, making twin… [EarthSky In AI-assisted UFO sighting investigation]earthsky.orgEarthSky | Updates on your cosmos and worldSun news: M5 flare erupts, sun-stuff may glance Earth · Visible planets and night sky guide fo…, Sirius matters because it repeatedly matches reports of a “stationary craft with changing coloured lights”. A large number of cases that initially sound unusual become much less mysterious once the reported direction, time and elevation are checked against the star’s position. The key investigative question is not whether Sirius can look strange — it absolutely can — but whether the sighting behaviour fits a fixed bright star distorted by Earth’s atmosphere.

Sirius illustration 1

Why Sirius is a repeat UFO suspect

Sirius is unusually effective at fooling observers because several independent factors combine at once.

First, it is exceptionally bright. Sirius has an apparent magnitude of about −1.46, making it the brightest star in the night sky. [Wikipedia]WikipediaSource details in endnotes. That brightness means atmospheric distortions are far more obvious than with dimmer stars. Tiny shifts in the air column become visible as dramatic flickers and colour changes.

Second, Sirius stays fairly low in the sky from the UK. Observers in Britain never see it pass overhead in the way southern observers do. Instead, its light travels through a much thicker layer of atmosphere, especially during winter evenings. [Sky & Telescope]skyandtelescope.orgsirius ly scintillating holiday12222014Sky & TelescopeHave a Sirius-ly Scintillating Holiday!22 Dec 2014 — Sirius twinkles more than most stars because it's bright, making twin… [Stargazers Lounge]stargazerslounge.comStargazers Lounge Why does Sirius sparkle with different colours?Observing23 Jan 2010 — Sirius twinkles because it is so low down to the horizon as seen from the UK. The light from it has to travel thro… The lower a star sits above the horizon, the more turbulence, haze, pollution, humidity and temperature variation its light must cross before reaching the eye.

Third, Sirius naturally attracts attention. It is bright enough to stand out through haze, urban light pollution and thin cloud. Witnesses who are casually scanning the sky often notice Sirius before they notice surrounding stars, which can make it appear isolated and artificial rather than part of a wider star field.

This combination produces classic UFO-style descriptions:

  • “A hovering object flashing different colours”
  • “A craft staying still but pulsing”
  • “A drone-like light changing from red to green”
  • “A stationary orb that suddenly sparkled”
  • “A bright object following me while driving”

Many reports become more understandable once investigators realise the witness was looking at a fixed celestial object near the horizon rather than a moving aircraft.

Astronomy writers and observing forums repeatedly note that Sirius is one of the most common astronomical sources of UFO misidentifications. [Cloudy Nights]cloudynights.comCloudy NightsAntares' particular blinking apearanceAugust 24, 2016 — 24 Aug 2016 — Take a look at Arcturus or Sirius sometime when they a…Published: August 24, 2016 [Sky Lens]sky-lens.comSky Lens Common Confusables — The Usual SuspectsCommon Confusables — The Usual Suspects - Sky LensSirius, Bright, rapidly twinkling, flashing red/blue/white near the horizon, Scintillat… Even astronomy communities regularly field questions from people convinced they are watching an unusual airborne object.

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Low-horizon colour flashing from the UK

The flashing colours are caused mainly by atmospheric scintillation and refraction. These effects become especially strong when Sirius is viewed through thick, unstable air near the horizon.

As the star’s light passes through moving pockets of air with different temperatures and densities, the atmosphere bends the light unevenly. Different wavelengths are refracted by slightly different amounts, briefly separating white starlight into red, blue and green components. Sky at Night Magazine [Sky & Telescope]skyandtelescope.orgsirius ly scintillating holiday12222014Sky & TelescopeHave a Sirius-ly Scintillating Holiday!22 Dec 2014 — Sirius twinkles more than most stars because it's bright, making twin… [EarthSky Because Sirius is so bright]earthsky.orgEarthSky | Updates on your cosmos and worldSun news: M5 flare erupts, sun-stuff may glance Earth · Visible planets and night sky guide fo…, those colour splits become obvious to the naked eye. EarthSky describes Sirius as effectively a “rainbow star” when low in the sky. [EarthSky]earthsky.orgEarthSky | Updates on your cosmos and worldSun news: M5 flare erupts, sun-stuff may glance Earth · Visible planets and night sky guide fo…

In Britain this effect is strongest during cold autumn and winter nights, especially:

  • over rooftops releasing heat
  • above cities with atmospheric pollution
  • near coastlines with unstable marine air
  • during frosty high-pressure weather
  • after sunset when temperature layers are shifting rapidly

Under poor seeing conditions, Sirius can resemble a flashing LED beacon more than a normal star. Observers frequently report rapid alternation between white, red, green and blue. [Sky at Night Magazine]skyatnightmagazine.comwhy do stars twinkle?2 May 2025 — Stars appear to twinkle because their light passes through our atmosphere and is bent and distorted by varying temperatures…Published: May 2025 [Sky at]skyatnightmagazine.comwhy do stars twinkle?2 May 2025 — Stars appear to twinkle because their light passes through our atmosphere and is bent and distorted by varying temperatures…Published: May 2025

The effect becomes even more dramatic through binoculars or phone cameras. Smartphone zoom exaggerates atmospheric instability and camera processing introduces additional artefacts:

  • autofocus pulsing
  • overexposure halos
  • digital sharpening
  • colour exaggeration
  • sensor noise
  • rolling-shutter distortion

As a result, witness video often appears more dramatic than the naked-eye view. A fixed star can look like a spinning orb or structured craft in compressed smartphone footage.

Sirius illustration 2

Why witnesses think the object is moving

Many Sirius-based UFO reports include claims that the object “darted”, “tracked the car”, or “hovered intelligently”. Darkness makes human motion perception unreliable, especially when there are few reference points.

Several normal effects create convincing movement illusions:

  • Autokinesis: a psychological effect where a fixed light appears to wander when stared at against a dark background.
  • Vehicle motion: while driving, a distant fixed light can appear to pace the observer.
  • Cloud gaps: moving cloud layers can make Sirius appear to emerge, disappear or shift position.
  • Eye motion: tiny involuntary eye movements create apparent drift.
  • Atmospheric shimmer: turbulence can make the star appear to jump slightly.

These effects become stronger when the witness is emotionally primed to interpret the light as unusual. Once a person suspects they may be seeing a drone, aircraft or UFO, the flashing colours and unstable appearance can reinforce that interpretation.

This is one reason Sirius reports often include confident statements that the object was “not a star”. The witness is describing genuine visual instability, but misidentifying its cause.

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How to test a Sirius match in a case file

In a UFO investigation workflow, Sirius is one of the fastest astronomical checks to perform. AI-assisted screening systems can often flag it automatically before deeper analysis begins.

A strong Sirius match usually includes most of the following features:

  • evening or pre-dawn timing
  • southern or south-eastern sky from the UK
  • low elevation above the horizon
  • object remained visible for many minutes
  • little or no true positional movement
  • flashing red, green, blue or white colours
  • witness filmed with heavy smartphone zoom
  • apparent “hovering”

Investigators can test the match using astronomy software, planetarium apps or automated sky reconstruction tools. The workflow is straightforward:

Sirius illustration 3

  1. Confirm the exact sighting time and location.
  2. Reconstruct the visible sky for that position.
  3. Check Sirius altitude and azimuth.
  4. Compare the witness direction with the star’s location.
  5. Examine whether the object remained fixed relative to landmarks.
  6. Review weather conditions and atmospheric stability.

If Sirius occupied the same sky position as the reported object, the explanation becomes substantially stronger.

An especially useful indicator is long-duration hovering. Witnesses sometimes report a mysterious flashing object remaining visible for 20 minutes or more. Conventional aircraft rarely stay fixed from the observer’s perspective for that long without obvious navigation lights or audible engine noise. A bright star can.

Cases where Sirius does not fully fit

A Sirius match should not be forced onto every flashing-light report. Some sightings genuinely involve aircraft, drones, planets, satellites or other phenomena. Others contain details inconsistent with a fixed star.

Investigators should treat the Sirius explanation as weaker if:

  • the object crossed large sections of sky
  • multiple independent witnesses observed structured motion
  • radar or ADS-B aircraft data contradict a star explanation
  • the object changed elevation rapidly
  • photographs show extended structure rather than a point source
  • the sighting occurred when Sirius was below the horizon
  • the witness accurately identified nearby stars but reported a separate moving object

This distinction matters in balanced UFO analysis. Sirius explains many reports well, but not all reports involving flashing lights.

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Why Sirius keeps returning in UFO culture

Sirius has become a recurring “usual suspect” because the visual effect is genuinely striking. Even experienced skywatchers sometimes stop and stare when the star is low and atmospheric conditions are unstable.

The important investigative point is that the witness is not necessarily imagining anything. The colours, flashing and shimmering are real optical effects produced by Earth’s atmosphere. What changes is the interpretation.

For AI-assisted UFO investigation systems, Sirius is therefore a high-value early-stage elimination check: easy to test, frequently relevant, and capable of explaining sightings that initially sound dramatic. When the reported object is stationary, brightly multicoloured, low on the horizon and observed during winter evenings in the UK, Sirius deserves immediate attention before more exotic explanations are considered.

Endnotes

  1. Source: earthsky.org
    Title: sirius the brightest star
    Link: https://earthsky.org/brightest-stars/sirius-the-brightest-star/
    Source snippet

    Although white to blue-white in color, Sirius might be called a rainbow star, as it often flickers with many colors.Read more...

  2. Source: Wikipedia
    Link: https://en.wikipedia.org/wiki/Sirius

  3. Source: sky-lens.com
    Title: Sky Lens Common Confusables — The Usual Suspects
    Link: https://sky-lens.com/guide/common-confusables
    Source snippet

    Common Confusables — The Usual Suspects - Sky LensSirius, Bright, rapidly [twinkling]({{ 'twinkling-stars/' | relative_url }}), flashing red/blue/white near the horizon, Scintillat...

  4. Source: earthsky.org
    Title: photo sirius in many colors
    Link: https://earthsky.org/todays-image/photo-sirius-in-many-colors/
    Source snippet

    Sirius in many colors | Astronomy Essentials15 Dec 2017 — These colors aren't intrinsic to the star, but instead result from refraction...

  5. Source: earthsky.org
    Title: the skys brightest star sirius before dawn
    Link: https://earthsky.org/tonight/the-skys-brightest-star-sirius-before-dawn/
    Source snippet

    EarthSkySee brightest star, Sirius, in your morning skyOct 29, 2025 — Sirius appears to flash different colors when it's low in the sky...

  6. Source: earthsky.org
    Link: https://earthsky.org/
    Source snippet

    EarthSky | Updates on your cosmos and worldSun news: M5 flare erupts, sun-stuff may glance Earth · Visible planets and night sky guide fo...

  7. Source: earthsky.org
    Title: colors scintillating venus mar 2017 photos
    Link: https://earthsky.org/astronomy-essentials/colors-scintillating-venus-mar-2017-photos/
    Source snippet

    Colors of scintillating Venus | Astronomy Essentials25 Mar 2017 — It has been low in the sky, where Earth's atmosphere has caused Venus t...

  8. Source: earthsky.org
    Title: Flashing star in autumn?
    Link: https://earthsky.org/astronomy-essentials/flashing-star-autumn-capella-arcturus-sirius/
    Source snippet

    Here are 3 candidatesOct 3, 2024 — Sirius appears to flash different colors when it's low in the sky. Really, all the stars are flashing...

  9. Source: earthsky.org
    Title: is sirius the most luminous star in the sky
    Link: https://earthsky.org/astronomy-essentials/is-sirius-the-most-luminous-star-in-the-sky/
    Source snippet

    Many people comment that they see Sirius flashing colors. This happens when you see Sirius low in the sky. The colors are...Read more...

  10. Source: skyandtelescope.org
    Title: sirius ly scintillating holiday12222014
    Link: https://skyandtelescope.org/astronomy-blogs/sirius-ly-scintillating-holiday12222014/
    Source snippet

    Sky & TelescopeHave a Sirius-ly Scintillating Holiday!22 Dec 2014 — Sirius twinkles more than most stars because it's bright, making twin...

  11. Source: meteorwatch.org
    Link: https://meteorwatch.org/sirius-twinkle/
    Source snippet

    It is very bright, which can amplify atmospheric effects.Read more...

  12. Source: stargazerslounge.com
    Title: Stargazers Lounge Why does Sirius sparkle with different colours?
    Link: https://stargazerslounge.com/topic/57590-why-does-sirius-sparkle-with-different-colours/
    Source snippet

    Observing23 Jan 2010 — Sirius twinkles because it is so low down to the horizon as seen from the UK. The light from it has to travel thro...

  13. Source: cloudynights.com
    Link: https://www.cloudynights.com/forums/topic/547826-antares-particular-blinking-apearance/
    Source snippet

    Cloudy NightsAntares' particular blinking apearanceAugust 24, 2016 — 24 Aug 2016 — Take a look at Arcturus or Sirius sometime when they a...

    Published: August 24, 2016

  14. Source: skyandtelescope.org
    Title: Sky & Telescope Why Stars Twinkle
    Link: https://skyandtelescope.org/astronomy-resources/why-do-stars-twinkle/
    Source snippet

    Sky & TelescopeWhy Stars Twinkle - Stellar ScintillationIt was proposed that stellar scintillation, could be due to the turbulence in the...

  15. Source: skyatnightmagazine.com
    Title: why do stars twinkle
    Link: https://www.skyatnightmagazine.com/space-science/why-do-stars-twinkle
    Source snippet

    ?2 May 2025 — Stars appear to twinkle because their light passes through our atmosphere and is bent and distorted by varying temperatures...

    Published: May 2025

  16. Source: skyatnightmagazine.com
    Title: green flash sirius
    Link: https://www.skyatnightmagazine.com/astrophotography/green-flash-sirius
    Source snippet

    Sky at Night MagazineSirius flashes green and twinkles as it sets in smartphone...16 May 2024 — The optical effect is to do with light f...

    Published: May 2024

  17. Source: skyatnightmagazine.com
    Title: twinkling star colours
    Link: https://www.skyatnightmagazine.com/astrophotography/astrophoto-tips/twinkling-star-colours
    Source snippet

    Photograph the changing colours of a twinkling starMar 2, 2021 — Follow our astrophotography guide to produce an image showing the changi...

  18. Source: skyandtelescope.org
    Title: The effect is even more vivid in binoculars. Steve Kluge.Read more
    Link: https://skyandtelescope.org/observing/sirius-ly-scintillating-holiday12222014/
    Source snippet

    Sky & TelescopeHave a Sirius-ly Scintillating Holiday!Dec 22, 2014 — The refraction of Sirius' starlight causes it to twinkle in every co...

  19. Source: youtube.com
    Link: https://www.youtube.com/%40earthsky

  20. Source: cloudynights.com
    Link: https://www.cloudynights.com/forums/topic/848356-newscaster-watch-sirius-for-pulsing-and-flashes-of-color/
    Source snippet

    Newscaster: "Watch Sirius for pulsing and flashes of color."30 Oct 2022 — When low in the sky it does appear to pulse and flash various c...

  21. Source: cloudynights.com
    Title: Sirius Scintillation
    Link: https://www.cloudynights.com/forums/topic/990613-sirius-scintillation/
    Source snippet

    General Observing and Astronomy18 Jan 2026 — Atmospheric turbulence causes twinkling of lesser stars. With really bright Sirius, a disco...

Additional References

  1. Source: reddit.com
    Link: https://www.reddit.com/r/askastronomy/comments/1fhig5z/a_flickering_object_in_the_northern_hemisphere/
    Source snippet

    A “flickering” object in the northern hemisphere: r/askastronomyI've tried googling it but all I could find is the star Sirius usually f...

  2. Source: facebook.com
    Link: https://www.facebook.com/groups/madisonastronomicalsociety/posts/24331316033141186/
    Source snippet

    Observing scintillation of star Sirius near horizonNormally this star is bright white in colour but when it is near the horizon it appear...

  3. Source: reddit.com
    Link: https://www.reddit.com/r/UFOs/comments/1k3wguz/what_is_this/
    Source snippet

    What is this??: r/UFOsIt's a star. Most likely Sirius. The flashing colors are called scintillation due to the earths atmosphere. Downl...

  4. Source: reddit.com
    Link: https://www.reddit.com/r/UFOs/comments/am7wmd/strange_flashing_star_what_is_this/

  5. Source: deepcreektimes.com
    Link: https://deepcreektimes.com/brightest-star-sirius-high-on-october-mornings/
    Source snippet

    Really, all the stars are flashing different colors, because light is composed of all the...Read more...

  6. Source: reddit.com
    Title: please take a look wth is this it keeps changing
    Link: https://www.reddit.com/r/UFOs/comments/1ifqpcq/please_take_a_look_wth_is_this_it_keeps_changing/
    Source snippet

    Please take a look! WTH is this? It keeps changing colourTime: sun/2/Feb/2025 5:35AM. Location: London- NW ~25° up. same object, seconds...

  7. Source: instagram.com
    Link: https://www.instagram.com/reel/DT_AhAzCInA/
    Source snippet

    and scatters the light, making it shimmer in different colors — similar...

  8. Source: reddit.com
    Title: Why doesn’t everything twinkle like Sirius???
    Link: https://www.reddit.com/r/Astronomy/comments/ihjjqb/why_doesnt_everything_twinkle_like_sirius/
    Source snippet

    r/AstronomyWhen I saw Sirius flickering and changing colors this morning I googled why. The accepted answer seems to be the refraction of...

  9. Source: physicsforums.com
    Title: why does sirius a blink in many colors.902706
    Link: https://www.physicsforums.com/threads/why-does-sirius-a-blink-in-many-colors.902706/
    Source snippet

    Why does Sirius A blink in many colors?5 Feb 2017 — Basically this happens due to atmospheric refraction and to every stars but Sirius is...

  10. Source: reddit.com
    Link: https://www.reddit.com/r/Damnthatsinteresting/comments/1kb6jwf/today_i_saw_sirius_a_brightest_star_in_the_night/
    Source snippet

    , and white because of a phenomenon called atmospheric scintillation...

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